Field of Invention
The present invention relates to a database storage system and method, and particularly relates to a storage system and method used for database backup.
Description of Related Arts
A database system usually consists of software and hardware. The software comprises a database management system (DBMS) and application program installed on an operating system. The DBMS is a kernel software of the database system and its main functions include definition and control of data, as well as creation, operation, management and maintenance of database. The hardware comprises a physical device forming a computer system which includes a server and a memory, and a peripheral device required to store database. The server provides a running environment for the operating system, and the memory provides a storage space for storing database. The storage device mainly used by the database is the magnetic disk and the magnetic disk array etc. So far, all database systems adopt the magnetic disk as a database-storage medium. The magnetic disk has the feature of high speed data access and easy expansion, and it is the best choice for real-time data processing.
However, the demand for high efficient response performance of the database system and the feature of physical structure of high speed operation of the magnetic disk device make Mean Time Between Failure (MTBF) of the system be not guaranteed for long time. When the scale of database becomes larger and larger, the reliability of the system declines rapidly by heavy use of magnetic disks. First of all, it will consume a lot of electric power to use large amounts of magnetic disks to store data. Taking a RAIDS magnetic disk array model as an example, the available capacity of five 2 TB high speed hard disks is about 8 TB, a database system with PB level needs at least 700 hard disks. In the case of solid state disk with smaller capacity, the number of solid state disks could be double. Therefore the magnetic disk is not appropriate for big data source. When the magnetic disk array operates, the power consumption is also considerable even if an energy-saving technology is used.
Because the content on the magnetic disk can be rewritten, the hard disk array cannot be used in the occasion required for higher security. The data on the magnetic disk are easy lost due to the physical damage of the magnetic disk, therefore a backup system must be configured to backup data in real-time or regularly. A real time backup system will also increase equipment investment and power consumption, while a regular backup system adopts often an incremental backup, and backups data in storage devices, such as the magnetic tape etc., the backed-up data cannot be read and used directly by the DBMS, the restoration time of backed-up data is long, and the normal operation time of the database system is affected during the restoration.
Therefore, the data that has not too high access frequency and must be preserved for long-term, as well as the data that belongs to being archived and preserved are not suitable for being stored using the magnetic disk storage device. With the rapid increase of file and data in various formats, the problems of their storage and use are challenging for the structure design of software and hardware of the database system.